The aim of our research is to understand the molecular mechanisms behind some basic functions of biological membranes. Towards this goal we are investigating the structures of selected membrane systems, using electron microscopy and diffraction methods of analysis. The systems being studied are: (1) Membrane-bound ribosomes. Earlier, we had determined how crystalline ribosomes are oriented on, and attached to, endoplasmic reticulum membranes. We are now characterizing their attachment further, correlating their configuration with that of membrane-bound ribosomes actively engaged in protein synthesis. We expect soon to establish some of the structural details associated with the process in which actively synthesizing ribosomes insert nascent protein into and through the lipid bilayer. (2) Gap junctions. In initial experiments, we produced two forms of isolated junction. These had different configurations for the connexon units, from which they are constructed. We have now determined how the forms relate to each other in three dimensions and are finding out if the different connexon configurations could be directly relevant to the mechanism by which gap junctions regulate the passage of small molecules between cells. (3) Membrane complex of Euglena. Euglena undergo striking repetitive changes in cell shape. Preliminary investigations indicate that these changes are the result of interaction between their regular cell membrane and regular underlying cytoskeleton. We are analyzing the structure of this complex to learn of the molecular details by which the membrane proteins and cytoskeletal components interact.